Thunderpants vs Custom IEMS

As far as a portable rig goes, how do the closed Thunderpants that Smeggy makes paired with an amp/dac like the Fostex HP-P1 Jude uses with it compare to custom IEMs like the Westone ES5 and the JH-16 straight out of an iPod or with an amp/dac in terms of sound quality and isolation? I have a feeling that these may replace some IEMs in portable rigs like some IEMs replaced open headphones.

cant tell you anything about sound quality comparison or type of sound signature, except that a guess would be that the sound signature of full sized closed orthos like the TP's is simply going to be different than the other IEM's mentioned.. even if they possibly were as good sounding (i dont actually know) i doubt they would sound very similar.